The common name for the gas used in balloons is helium. Helium is a lighter-than-air, non-toxic gas that provides the buoyancy needed for balloons to float. It is the second lightest and second most abundant element in the universe. Helium is preferred over hydrogen for filling balloons because it is much safer; hydrogen is flammable and poses a risk of explosion. Helium is often used not just in party balloons but also in scientific applications, including cryogenics and as a lifting gas for blimps and scientific research equipment. Its unique properties make it indispensable in various fields.